The present application is related to balloon type catheter devices, and more particularly to a method and apparatus for forming, wrapping and compressing balloons to provide a reduced profile catheter configuration.
Angioplasty has gained wide acceptance in recent years as an efficient and effective method for opening stenosis in the coronary arteries and in other parts of the vascular system. The most widely used form of angioplasty makes use of a dilatation catheter which has an inflatable balloon at its distal end. Using fluoroscopy, the physician guides the catheter through the vascular system until the balloon is positioned across the stenosis. The balloon is then inflated by supplying a fluid under pressure through an inflation lumen to the balloon. The inflation of the balloon causes stretching of the artery and pressing of the lesion into the artery wall to reestablish acceptable blood flow through the artery.
Intra-aortic balloon catheters have also gained wide acceptance in recent years. Intra-aortic balloon catheters are typically inserted into the aorta of the heart, often percutaneously, and then inflated and deflated out of phase with the natural pumping action of the heart. By doing so, the intra-aortic balloon catheters can supplement the natural pumping action of the heart. Both dilatation catheters and intra-aortic balloon catheters are balloon type catheters devices.
One important characteristic of balloon type catheters is the distal xe2x80x9cprofilexe2x80x9d, which is determined by the outer diameter of the distal end portion of the balloon when deflated. This outer diameter affects the ease and ability of the catheter to pass through a guide catheter, through the coronary arteries and/or across a tight lesion. Considerable effort has been spent in developing low profile balloon type catheters by minimizing the dimensions of the core or inner tube which extends through the balloon to its distal end, and by reducing the wall thickness, to the extent possible, of the balloon itself.
A complicating factor in minimizing the deflated profile of a catheter balloon is that the balloon membrane is often not distensible, i.e. it does not stretch or contract in response to changes in internal pressure. This is typically true for both dilatation catheters and intra-aortic balloon type catheters. Thus, the balloon membrane typically has a constant surface area regardless of whether the balloon is inflated or deflated. To reduce the outer diameter of the balloon catheter in its deflated condition, it is common to fold the balloon flat, so that two wings are brought together in some fashion, as by folding or wrapping, so as to reduce the overall diameter of the deflated balloon. In use, the inflation fluid that is applied to the folded balloon causes the flaps to unwrap so that the balloon can inflate to its full inflated state.
While it is desirable to minimize the profile of the catheter, it is also desirable to provide a large inflated outer diameter to the balloon. As the inflated outer diameter is made larger, the flaps of the balloon become relatively large relative to the core or inner tube of the catheter. The result is that it is often difficult to eliminate the interstitial space between the flaps when folded together or wrapped around the catheter.
Various methods and balloon configurations have been proposed in the prior art for providing a balloon type catheter that has the lowest profile possible when deflated and the largest possible diameter when inflated. One approach, which is suggested, for example, in U.S. Pat. No. 5,087,246 to Smith and in U.S. Pat. No. 5,147,302 to Euteneuer et al., is to provide a dilatation balloon having more than two flaps or wings (for example, three wings) such that when the flaps or wings are wrapped circumferentially, the distance that each flap extends around the catheter is reduced when compared with the two flap configuration. The ease with which such flaps fold is also enhanced when the number is increased, such that when the balloon is deflated and withdrawn through the guide catheter following a procedure, the balloon more readily returns to its wrapped condition. The result is a reduced deflated profile given the same inflated diameter.
Typically, the balloon flaps are formed during the manufacturing process of the catheter. U.S. Pat. No. 5,350,361 to Tsukashima et al. discloses a method for preparing a tri-fold balloon configuration. Tsukashima et al. initially impart the tri-fold configuration to the balloon by inflating the balloon in a longitudinal interstitial channel defined by three substantially cylindrical pins arranged in a pyramid-type stack. While the balloon is secured in this channel, negative pressure is applied to an inflation lumen of the balloon to deflate the balloon, thus providing the tri-fold configuration to the balloon.
The balloon may be xe2x80x9cheat setxe2x80x9d in the desired fold configuration so that the balloon returns to the fold configuration when the balloon is deflated. Tsukashima et al. suggest heating the creases defined by the three tri-fold flaps with a longitudinal heating element. This apparently softens the balloon material in the longitudinal creases, so that the same creases will tend to form whenever the balloon is deflated.
Once the flaps are formed and/or set in the balloon, it is common to manually fold the balloon flaps circumferentially around the catheter. The flaps are then typically held in place with a balloon protector. A balloon protector typically serves two functions. First, the balloon protector protects the balloon and the distal tip of the catheter from possible damage during shipping. Second, the balloon protector wraps the balloon tightly in its deflated condition to minimize the outer diameter of the balloon in its deflated state.
A typical balloon protector is applied to the distal end portion of the catheter prior to packaging and sterilization of the catheter. The sterilization process often involves exposing the catheter, with the balloon protector in place, to an elevated temperature for a predetermined time period. With certain balloon materials, such as polyolefin, the sterilization process causes the balloon to be xe2x80x9cheat setxe2x80x9d in the folded or wrapped condition in which it is held by the balloon protector. As a result, when the balloon protector is later removed, the balloon tends to remain in the tightly wrapped condition.
To further reduce the profile of the wrapped balloon, the balloon protector can be constructed to be radially compressible. This further reduces the interstitial space in the wrapped balloon particularly during the heat setting process. Thus, when a balloon material is used that exhibits heat set characteristics, the deflated balloon will tend to remain tightly compressed even after removal of the balloon protector.
While the prior art provides some improvement in the field of folding, wrapping and compressing balloon type catheters, there are still a number of limitations, some of which are discussed below. One limitation is that the prior art balloon flaps are typically manually folded over the catheter by an operator during the manufacturing process. This can be a relatively slow and tedious process, and the quality of the wrap is often dependent on the skill of the operator. Second, the balloon protector must typically be installed over the wrapped balloon, which can also be a slow and tedious process. It would be desirable, therefore, to provide an apparatus and method that helps form, wrap and compress the balloon flaps during the manufacturing process.
It would also be desirable to provide a tool that could be used by a physician during a medical procedure to reform the flaps and rewrap the balloon. It has been found that once a balloon has been inflated to relatively high inflation pressures, the balloon material can loose the heat set characteristics provided during the manufacturing process. For example, a tri-fold balloon that has been inflated to relatively high pressures (10-15 atm) may take on a pancake shape having, for example, only two flaps when deflated. Further, the balloon may not return to the original low profile wrap configuration. This can prohibit the crossing of additional lesions using the same catheter. To reach other lesions, the physician must often withdraw and discarded the catheter in favor of a new catheter that has a balloon that was tightly wrapped during the manufacturing process.
The present invention overcomes many of the disadvantages of the prior art by providing a method and apparatus for sequentially forming, wrapping and compressing a catheter balloon during the initial manufacturing process and/or during a subsequent medical procedure. In either case, the balloon may be formed, wrapped and compressed by simply advancing the balloon through a balloon wrapping tool, and selectively inflating and deflating the balloon therein according to the methods described below.
In one illustrative embodiment of the present invention, the balloon wrapping tool includes a flap forming section, a flap wrapping section and a flap compression section. The flap forming section has a flap forming bore extending therethrough that is shaped to produce at least two flaps in the balloon when the balloon is inflated and subsequently deflated therein. The flap wrapping section, which is preferably positioned adjacent to the flap forming section, has a flap wrapping bore extending therethrough that is axially aligned with the flap forming bore and shaped to wrap the at least two flaps around the catheter as the deflated balloon is advanced therethrough. The flap compression section is preferably positioned adjacent to the flap wrapping section, and includes a flap compression bore extending therethrough. The flap compression bore is preferably axially aligned with the flap wrapping bore to receive the wrapped balloon. The wrapped balloon may be inflated and deflated in the flap compression bore to compress the wrapped balloon and to set the creases therein.
An illustrative method of the present invention includes the steps of: inflating the balloon in the flap forming bore; deflating the balloon in the flap forming bore to produce the at least two flaps in the balloon; and advancing the deflated balloon into the flap wrapping bore to wrap the at least two flaps around the catheter as the deflated balloon is advanced therethrough to provide a wrapped balloon. The illustrative method may further include the steps of: advancing the wrapped balloon into the flap compression bore; inflating the wrapped balloon while in the flap compression bore; deflating the wrapped balloon while in the flap compression bore; and removing the wrapped balloon from the flap compression bore.
In one illustrative embodiment of the present invention, the balloon wrapping tool is initially separated from the catheter, and advanced in a proximal direction over the distal end of the balloon. In this embodiment, the flap forming section is proximal of the flap wrapping section, and the flap wrapping section is proximal of the flap compression section. Once the balloon is positioned in the flap forming section, the balloon is inflated and deflated, as described above. The balloon wrapping tool is then advanced proximally until the balloon is in the flap wrapping section, and finally in the flap compression section. Once the balloon is successfully formed, wrapped and compressed, the balloon wrapping tool is slid distally off the distal end of the catheter.
In another illustrative embodiment, the balloon wrapping tool is advanced in a distal direction over the balloon. In this embodiment, the balloon wrapping tool is preferably provided in a coaxial arrangement with the catheter shaft, and releasably secured to the manifold of the catheter. Accordingly, the flap forming section is positioned distal of the flap wrapping section, and the flap wrapping section is positioned distal of the flap compression section. In this configuration, and after the balloon has been inflated during a medical procedure and subsequently withdrawn proximally from the body, the balloon wrapping tool is released from the manifold and advanced distally over the catheter shaft until the flap forming section of the balloon wrapping tool is positioned over the balloon. The balloon is then inflated and deflated to form the desired flap configuration in the balloon. The balloon wrapping tool is then advanced distally until the balloon is provided in the flap wrapping section, and finally in the flap compression section. Once the balloon is successfully formed, wrapped and compressed, as described above, the balloon wrapping tool may be slid off the distal end of the catheter and discarded.
In another illustrative embodiment of the present invention, the balloon wrapping tool includes, from the proximal end to the distal end, a flap forming section, a flap wrapping section, a flap compression section and another flap wrapping section. As described more fully below, this illustrative embodiment may be particularly useful for wrapping and/or rewrapping the balloon of single operator exchange type device. In a single operator exchange type device, the guide wire typically only extends from a proximal guide wire port, through the balloon, to a distal guide wire port. The proximal guide wire port is typically located just proximal of the proximal end of the balloon. It is known that the guide wire typically provides significant column support for the catheter shaft. Since the guide wire only extends through a distal portion of the single operator exchange type device, the catheter shaft just proximal of the proximal guide wire port may have a reduced column support.
To properly form the balloon, the flap forming section of the balloon wrapping tool preferably has a length that is at least as long as the balloon. When the balloon is advanced into the flap forming section or the compression section, the operator or physician may not be able to grasp the catheter near the proximal guide wire port. Because of the lack of column support, and the inability of the operator or physician to grasp the catheter sufficiently close to the proximal guide wire port, it may not be possible to advance the balloon of a single operator exchange type device into the flap wrapping section and/or flap compression section, as described above.
Accordingly, after the balloon is inflated and deflated in the flap forming section, the balloon may be withdrawn from the balloon wrapping tool. The balloon may then be inserted into the second flap wrapping section, which in this embodiment, is located on the opposite side of the compression section from the flap forming section. Alternatively, the flap wrapping section can be adjacent to the other sections. Since no flap forming section is provided adjacent to the second flap wrapping section, the operator or physician may grasp the catheter shaft near the proximal guide wire port, and provide the needed column support. Thus, the operator or physician may advance the balloon into the second flap wrapping section and the flap compression section to complete the forming, wrapping and compression of the balloon.